This invention relates generally to composite box structures which may be used in the manufacture of various types of railway cars and more particularly to composite box structures formed from individually molded components.
Over the years, general purpose railway boxcars have progressed from relatively simple wooden structures mounted on flat cars to more elaborate arrangements including insulated walls and refrigeration equipment. Various types of insulated railway boxcars are presently manufactured and used. A typical insulated railway boxcar includes an enclosed structure mounted on a railway car underframe. The enclosed structure generally has an outer shell, one or more layers of insulation and interior paneling. The outer shell of such railway boxcars often has an exterior surface formed from various types of metal such as steel or aluminum. The interior paneling is often formed from wood and/or metal as desired for the specific application. For some applications, the interior paneling has been formed from fiber reinforced plastic (FRP). Various types of sliding doors including plug type doors are generally provided on each side of conventional railway boxcars for loading and unloading freight. Conventional railway boxcars are assembled from various pieces of wood, steel and/or sheets of composite materials such as carbon fiber reinforced plastic. Significant amounts of raw material, labor and time are often required to complete the manufacture and assembly of conventional railway boxcars.
The underframe for many railway boxcars includes a center sill with a pair of end sills and a pair of side sills arranged in a generally rectangular configuration corresponding approximately with the dimensions for the floor of the railway boxcar. Cross bearers and cross ties are provided to establish the desired rigidity and strength for transmission of vertical loads from the side sills to the center sill and for dissipating horizontal end loads on the center sill to other portions of the underframe. A plurality of longitudinal stringers is also provided on each side of the center sill to support the floor of the enclosed structure. Examples of such railway car underframes are shown in U.S. Pat. Nos. 2,783,718 and 3,266,441.
For many years various techniques have been used to build fiberglass boat hulls. Many of these hulls have been fabricated using wet layup techniques in which each layer of material such as carbon fiber or carbon fiber is first wetted with the desired resin such as polyester or vinylester and then laid in an open mold. Recently, vacuum bagging techniques have been combined with wet layup techniques to control the emission of volatile organic compounds. Vacuum bagging also produces a stronger structure by eliminating air pockets and excess resin in the finished product.
More recently, vacuum bagging techniques have been combined with an enhanced resin delivery system which allows the use of a closed molding system and dry layup of core layers and fiber reinforcing layers such as carbon fiber in the mold. This process may sometimes be referred to as composite resin infusion molding. U.S. Pat. Nos. 4,902,215; 5,052,906 and 5,316,462 provide additional information concerning this type of vacuum bagging process to form a carbon fiber reinforced composite article.
Various types of load dividers and freight securing systems have previously been used to prevent undesired movement of freight contained within a railway boxcar. The use of such systems is particularly important when a railway boxcar is only partially loaded. Examples of such systems are shown in U.S. Pat. No. 5,370,482 entitled Cargo Securement System and U.S. Pat. No. 5,386,674 entitled Two Piece Bulkhead Door for Rail Cars and the Like.
In accordance with the present invention, disadvantages and problems associated with previous composite box structures used to manufacture various types of railway cars have been substantially reduced or eliminated. The present invention provides composite box structures for various types of railway cars including, but not limited to, railway boxcars and temperature controlled railway cars. The composite box structure provides enhanced insulation, reduced weight, increased load carrying capacity and increased service life as compared to conventional railway cars. A composite box structure formed from individually molded components incorporating teachings of the present invention allows manufacture and assembly of the resulting railway boxcar with substantially reduced costs as compared to conventional railway cars with the same performance characteristics and as compared to composite box structures formed by integrally molding several components as one or more composite units.
A composite box structure formed from individually molded components incorporating teachings of the present invention allows combining a temperature control system with an airflow management system to provide a temperature controlled boxcar with substantially reduced total lifetime costs as compared to conventional refrigerated boxcars with substantially the same performance characteristics. The composite box structure provides enhanced insulation, reduced weight, increased load carrying capacity, better temperature regulation and increased service life as compared to a typical refrigerated boxcar.
One aspect of the present invention includes a composite box structure having a roof, sidewalls, endwalls and a floor fabricated as individual components using vacuum bagging techniques along with dry layup of selected material layers and an enhanced resin delivery system. The individual components may then be assembled with each other using adhesives and/or mechanical fasteners to form the desired composite box structure. The present invention also allows using the same individually molded component such as an endwall or a sidewall to form various types of composite box structures. Thus, increasing the utilization of the associated molding system and decreasing the unit cost for each individually molded component.
For some applications, each sidewall is preferably formed from a first section and a second section. Each section has a generally rectangular configuration. The respective first section and the second section of each sidewall are preferably spaced from each other to form an opening corresponding with the desired location of a door for the resulting railway boxcar. As a result of forming a composite box structure in accordance with teachings of the present invention, the cost and time required to complete the molding process for the individual components and assembly of the resulting composite box is substantially reduced as compared with the time and cost required to integrally mold sidewalls and endwalls with the floor and/or roof.
Another aspect of the present invention includes a box structure having a roof, sidewalls, endwalls and a floor fabricated as individual components using molding techniques to form selected components from composite materials and conventional railway car manufacturing techniques to form other selected components from wood and/or metal. For example the roof and floor of a box structure may be formed from composite materials using various types of molding techniques. The sidewalls, endwalls and/or doors may be formed from wood, steel and other materials associated with conventional railway boxcars.